Headlight-lens.



Patented 061.9, |900.

3 shuts-Sheet 2.

Y J. H. PITKIN.

HEADLI'GHT Lens. (Applimion med my 11, 1900.,v

(No M'ocllel.)

Patented Oct. 9, |900.

.. J. H.' PIT-KIN.,`

H EADLIGHT LENS. (Application led May 1}, 1900.)

(No Model.)

3 sheath-shea: 3.

f Kc? 6am/@A 5 als s, v

' [UNITED STATES-f" .PATENT CE1-Inns JULIAN-rn. PITKIN, or CHICAGO,ILLINOIS; Y i\ H EADeLr-GHT- LNS;

SPECIFICATION' forming pare of Letters Patentino. 659.353, dated oceoeere, 1900.

A y Application tiled May 1l, 1900. Serial No.-16,822. (No modell To allwhom it may concern: l extended 'laterally-confined path along the Be itknown that I, JULIAN H. PITKIN, of ground. and the angle as between theprisms Chicago, in the county of Cook and State of themselves'is alsovaried, all as will hereins 5 Illinois, have invented certain new anduse- 'after more clearly appear. f 5 ful Improvements inlieadlight-Lenses,l of v In abicycle headlight-lens there are emwhichthe following is a specification. I ployed a series of prisms arrangedconcen- My invention relates to lenses for v'ehiclctrically and whichoccupy substantially the headlights, and has for its object to providewholeof the surface of the lens,.the prisms 6o such a device that willassemble and conne beging arranged close to each other. The rays 1o therays of light in a beam that shall be lim- 'of light proceeding from theflame diverge or ited laterally to a narrow path and extend spread, andwhen these divergent rays pass along the-ground from a point in closeproxthrough the plane emergent surfaces of adjaimity to the source oflight to a point considcent prisms it is found that this divergence 65erably distant therefrom without at the same is not corrected and therefracted rays 4of light 'I5 time crossing the line of vision. fromadjacent prisms intercept each other, v My improved lens is primarilyintended'for` thus producing a pen-umbra or shadow at the use onbicycle-lamps, where a thoronghlysides of the lin'e ofintersection*ioovercome---v illuminated path from the wheel to a distantthis defect is another object of myinvention,` 7o point ahead isessential in order that the. and this Ido by providing prisms whoseemer- 2o character of the ground may b e revealed to gent surfaces arenot plane, but, on the conenable the rider to avoid obstructions andtrary, are slightly convex or curved in crossconsequent danger ofinjury, though it may section. l g 'be applied to any vehicle-headlight.It is :In the accompanying drawings, Figure 1 75 desirable in order tosecure the best results is 'a face' v iew of my improved leus. Figs. 2,z5 that the entire number of light-rays be util- 3, and 4 are sectionson the lines 2 2, 3 3, and

ized and concentrated throughout the path 4 4. Fig. 5 represents aseries of cross-secto be illuminated, which in the ordinary bitions ofthe same prism, showing the varial cycle headlight-lens is-not the case.The ob- A tion in the angle at different portions there- 8o jection' tothe ordinary lens in use is that it of.. Fig. 6 is a horizontal sectionof the lens,

3o either illuminates a widearea close to the showing the light-rays bydotted lines. Fig. wheel, while the road .in front is left in dark- 7 isa vertical cross-section, the dotted lines ness, or it illuminates aspotat some distance showing the paths of.,the incident and emerahead, whilethe road immediately in front of gent rays of light; and Figs. 8 and 9are ver- 85 the wheel remains dark, in either of which tical sectionalviews showing, respectively,'a

35 cases the probability of revealingan obstruclens having prisms withcurved emergent tion in the road under conditions that will surfacesanda lens having prisms with plane enable the rider to avoid it aregreatly diminemergent surfaces, with diagrammatic illusished ascomparedv with a lens such as I have trations' of the effect of saidconstructions 9o devised that will throw a continuous beam upondiverging rays oflight.

4o of light from the Wheel to a remote point in The lens `is preferably,though not necesfront. l sarily, made circular in form, and it may be Bymy improved lens the rays of light are cast or molded in one piece forconvenience concentrated to strike the ground close to the inmanufacture. 95 wheel and to extend in a 'laterally-confined Inconstructing this improved lens advan- 45 path from that point alongtheground to a tage is taken of the well-known property of considerabledistance ahead. These desirable the prism to deflccta ray of light as itpasses results are secured by constructing the lens therethrough firsttoward the normal of theinof prisms whose angles of refraction vary incident surface and then as it passes from the roo different portions ofthe same prism-that is, dense medium of the prism into the less dense 5oeach prism is so constructed that the angles airaway from the normalofthe emergent surof refraction at different portions thereof shallface. The direction of any ray of light may be such as to direct therays of light in an thus be controlled as to its direction of refractionby simply changing the angle of the prism through which it passes. It inthe same prisin the angle is uniform-that is, if the angle between theincident and emergent surfaces is the same throughout-the direction ofthe retract-ed rays will be the same,

`whereas if this angle's made to vary the direction of the retractedrays will likewise vary', and I have taken advantage of this fact to sovary the angle of the -pris'uis -at dierent parts thereof as that tberays of light will be directed in a continuons path along the ground,and Ihave so varied the inclination ot the prisms as between themselvesthat the path shall extend from the wheel continuously to' a greatdistance ahead.

In the drawings the lens A, shown preferably as circularin shape, hasany usual or desired form of center B, either plane or eenvex, and isprovided with a series ot contini nous prisms a, a', a?, a3, and a4 ot'any desired number which are preferably shown as annular in foidn,though, as it is quite obvi-l ous, they might be made oval, elliptical,or of anyot-her continuons contou r, and when I use the term annular inthe specitication and claims I mean of any continuous contour, as herereferred to.

v the emergent surface C at the bottom of the lens is quite small, asrepresented at f l/, and at the points of the prism between the top andbottom the angle ot the prism, as l will term the angle between theincident and emergent surfaces, varies between :n and y. This variationin angle is well delincd4 in the cross-sections of Fig. l represented byFigs...

2', 3, 4, and 5. In the vertical cross-section 4 ot liig. 2 the anglesof the prisms at theitop of the lens are the maximum desired, whilethose at 'he bottom nl' t-ho lens in the same prism are the minimum inthat prism. The cross-section represented by Fig. 3 beinghorizontal, theangle of the several prisms is intermediate ora mean between the angleol` the same prism at the top and bottom, while Fig.

4, being a section midway between t-hc hori- -j-zontal and Vertical onthe line 'i l of liig. l,

shows the angles ot' the prisms at the top and bottom intermediate oramean between the angles ol` the same prisms in the vertical andhorizontal sections.

lt will be clear from the above that nach prism varies'in angle from thetop to the bottom of t he tens and that the. angles ol'l adjacentportions ol' thesamc prism ditler-tbatis,tl1c angles ot the prisms inthe vertical section ot' l"ig. L dller trom the angles ol' the sameprisms Aon through the entire series of prisms.

in the section ofthe adjacent. portion in Fig. 4. The eteet of lthisvariation of angle i-n the saine prism is to retract the rays of lightdifferently at different portions of the same prism. For instance,having reference to Fig. 7, let L represent a source of light. Then therays striking at Z will be retracted by the emergent surface b in thedirection of m, which would intersect the ground at a long distance fromthe lens, t'vbile the refraction of tbe rays striking the incidentsurface at Z9 will be in the direct-ion of m9,which would intersect thegronn d ata point close to the lens, and the direction of raysratintermediate points t and l in the same prism will vary according to theanele of the prism* at those points and will be intermediate thedirections of m and m9.

It the several prisms were similar or uniform in their inclination, (it,in other words, the prisms a, c', a2, afi, and ai on the cross-scctionsof Figs. 2, 3, and i were of the like or similar inclination,) thetendency would be to direct the rays approximately in the same directionas the prism a. just described, with the resulting etfect ofilluminating the periphery ot' an oval or ellipse upon the ground,leaving a relatively dark center. To, obviate this, I have varied theangles of the prisms as between themselves-that is, on correspondingportions of adjacent prisms the angle ot' one prism differs from theangle of the other prisms. Referring to Figs. 2, 3, and t, it will benoticed, that the prism a on the cross-sections shown has a larger anglethanprism a', that prism a.' has alargerangle than prism 11.2,' thatprisln a2 has a larger angle than prism o3, and so 0n with the entireseries ot'A prisms. The result is that while a ray of light entering theprism a at l is by its retraeting-snrface I) directed toward m, a rayot' light entering the prism a at Z is by its refraetng-surtace b'directed to m, the ray entering at I2 is directed by the surface h2toward m2, and so 'lhe rayscntering at 3, l, li", l", 7.7, ZH, and l aredirected by the surfaces 03,021?, Il, (i7, Il, and b", respectively,toward the points m3, m4, 'l'lt5,nL,-nl7,111.8,and nl." inslightly-divergent paths, so that while the ray of light emerging atsurface I is directed to the most distant point and tho ray emergingl'rom surl'aec In is directed to the ground close to the lons at nl. therays elm-.rging from the intermediate prisms strike the ground one inadvance ol' the other, thus forming a continuons path of light from thewheel to themostdistmit point reached bythe retracted ray :it surllieel.

ly reference t0 Fig. ti il will he seen that the angles ol' dillerentportions o" the same prism on oppositesidesot' the center lot' the lensare the same, so that theI rays ol` light emerging l'rom the surface ot.prism o on either side ol' tho center ol` theylens are directed innearly parallel paths and l'orm the outer horizontal boundaries ot' thebeam of light, while the several prisms varying iu augie as betweenthemselves diret-tibo rays to YOC IIO

light up the entire path between the outer or boundary rnys.

In Fig. I have shown n. single prism and at different portions thereofhave illustrated vis represented es of seventeen degrees; at f 3,

- thirty degrees; .tt f2, thirty-seven degrees;

at f' and at f,'the point of greatest angle, forty-four degrees. Ofcourse these angles may be varied within wide limits; but theillustration is explanatory of the general char.- acter of the prisms.

Figs. 8 and 9 are diagrams showing two forms of lens. The former figureshows a. lens having prisms whose emergent surfaces are curved nud thelatter prisms whose emergent surfaces are plane, said figuresillustrating the loss of light due to interference of the ref rnctedrays and its remedy. This "estore of my invention has for its object toprevent the interference of the rays of light, and the loss consequentof such interference is clearly illustrated in these figures. The ra-ysof light proceeding from the source L diverge and upon emerging from theprism shown in Fig. 9 are still divergent.,^owing to the fact that saidrays enter the incident surface at an angle and ere refrncted also at anangle corresponding to their angle of divergence.

From an inspection of the diagram Fig. 9 it will be seen that the raysof light refrncted f rom the lower one-third o ofthe upper prism and theupper one-third o of the next adjacent prism intercept each other, andthe effeet is to produce in lines at each side ofsaid points ofinterception areas of darkness.

By making the emergent surface of the prism ofn slightly-curved formtransversely, as shown in Fig. S, this fault is corrected and the rnysof light are refrncted in parallel lines, avoiding the darkening.

llnving thus described' my invent-ion, what I claim, :nul lesire tosecure by -Letters Pntcnt, is-

l. A lens for vehicle-headlights, having a continuous prism, the angleof Whose emer- 5o gent surface varies throughout the length thereof.

2. A lens for vehicle-headlights provided: with a. series of continuousannular prisms,

the a-ngle of each of which varies throughoutthe prism.

3. A lens for vehicle-headlights providedj A 5. A lens forvehicle-headlights provided with a. series of continuous annular prismsvarying in angle as between themselves, and the angle of each of whichvaries throughout the prism.

6. A lens for vehicle-headlights provided 7o with a. series ofcontinuous annulmprisms varying in angle as between themselves, and theangle of each prism varyingcontinuously from the bottom to the top ofthe lens.

7. A lens for vehicle-headlights having a' 75 series of continuousannular prisms arranged on one face thereof, the angle of each of whichvaries throughout the prism, the incident su rface of a-ll the prismsbeing in the seme plane.

8. A lens for vehicle-headlights having a. 8o

continuous prism, the angle of whose emergent surface varies throughoutthe length of the prism, said prism havingits emergent surface curvedtransversely.

9. A lens for vehicle-headlights having a plurality of prisms arrangedconcentric to each other and to the source of light, and the angle ofwhose emergent surfaces varies throughout the length of the prisms, saidprisms having th ei r emergent surfaces curved 9o trans versely.

JULIAN n. rrrmN.

Witnesses:

A. C. CORNING, Cit/xs. S. PrrKiN.

